Temperature control of the FP-cavity length, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics 
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today with Fatematuj, we did a long-term frequency drift measurement between the FP-cavity loaded with 50kW and the RF reference frequency... and without
any other thermal source (no heating cable !)
we had a small lock loss at t ~ 120mn. |
Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this morning, I shut off all the equipements (especially the computer) except the ones powered by the UPS : laser controller, laser peltier controller,
laser motors controller.
and I disconnected the cables from the power plugs of the wall (to prevent any possible overvoltage). |
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Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this afternoon, I checked visually what happens when the AC power of the UPS is broken down => the laser controller has still its "emission"
button ON... no AC interruption.
so, I guess the UPS switched properly the output AC line from the input AC line to the internal batteries. |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this morning, I plugged back the 4 power cables which supply all the equipments.
all the equipments have restarted without problem, but the shutter of the laser amplifier needs a ThomX safety system grant to let the beam propagate
to the cavity... |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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the laser coupled into the amplifier is still measured at ~3mW at the input, on the Alphanov software, once the Amp stage are started at 0% of power
ratio.
this afternoon, Kevin restarted the 3rd safety system of ThomX to grant the opening of the beam shutter => now the shutter can be opened. |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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this morning, I set the Ring frequency at 500.25MHz and after switching ON the power supply of the amplifiers for the RF signal coming from the laser,
I saw the beating frequency (between ring RF and laser harmonic frerquencies at 500.25MHz) that I canceled, playing with the Smaract motor.
Now, I need to adjust the FP-cavity length to follow the laser cavity length but the IcePap DS (controlling the FP-cavity motor) freezes too |
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Restarting equipements after Christmas shutdown, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics | software
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on last friday (12/01/2024), the IcePap DS issue was solved and I was able to control the FP-cavity motors properly.
I was able to quickly lock either the laser on the FP-cavity and the FP-cavity on the RF reference as before.
then, we can close these posts on restarting the equipments after the Christmas shutdown |
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33MHz (FP-cavity vs RF) phase stability, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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this morning, with Vincent Chaumat, we made a beating (phase detection) between the laser 33MHz and the 33MHz coming from the Rigol generator locked
by the 10MHz link onto the 500MHz ring generator.
once the laser and the FP-cavity are locked on the RF reference, the 33MHz phase detection is stabilized and confirm the laser/FP-cavity lock |
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Adding one photodiode in reflection, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this morning, I added a DET36 photodiode in reflection (I used a thin beam splitter) to better measure the coupling over the full beam size.
this DET36 photodiode is sent to the "laser locking" oscilloscope with the other signals :
CH1 :transmission |
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controller M1 & M4 (plan mirrors) with IcePap controllers, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | cabling
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previously, we have connected motor M4 with an IcePap controller.
see this post : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/278
due to the backlash behavior of the FP-cavity motors, it is impossible to work in both directions on one motor when the FP-cavity is locked. |
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controller M1 & M4 (plan mirrors) with IcePap controllers, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | cabling
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this double motors scheme works good.
if motor P4 is used by increasing value, the FP-cavityPZT signal (pink signal on scope) goes HIGHER
if motor P1 is used by increasing value, the FP-cavityPZT signal (pink signal on scope) goes LOWER |
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First stable X-rays production, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this morning, we locked the laser on the FP-cavity with about 48-49kW stable in the FP-cavity (for 32% of amplifier ratio).
and then we locked the FP-cavity on the RF reference (500MHz beating lock + 33MHz beating for starting lock search).
the starting lock search voltage has been chosen between -20mV and +20mV. |
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controller M1 & M4 (plan mirrors) with IcePap controllers, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | cabling
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at the begining of each session, it will be mandatory to avoid any backlash for the motors :
- for the P4 motor : one can go 2k steps DOWN, then 2k steps UP to go back to -360 000 and use the
steps UP without any backlash |
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33MHz (FP-cavity vs RF) phase stability, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, I locked the laser on the FP-cavity and the FP-cavity on the RF reference with 47kW inside the FP-cavity.
equivalent jitter :
when lock is OFF : sine signal V=V0*sin(phi(t)) with V0=300mV => Vrms = 300/sqrt(2)) = 210mV rms |
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locking, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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during the last days we changed the FP-cavity - RF reference locking system to force the right bucket:
in addition to the 500MHz beating which is the signal input to the PID, we added a 33MHz beating signal which is the trigger signal of the PID.
then, the lock is triggered only when this trigger signal is close to 0. |
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Laser cavity temperature/pressure sensitivity, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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this morning, I did a 500MHz beating frequency (Laser vs RF) drift test with the Smaract motors configured with "Sensor Mode" OFF over 50 minutes
(~ 1500 acquisitions)
compared with previous measurements, one observes a much more smooth "exponential-like" drift compared to "Sensor Mode" ON |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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This morning with Daniele, we changed the laser/RF locking scheme :
1) we use the laser 33MHz internal photodiode to do some beating with the 33MHz RF generator (A Rigol generator locked on the 500MHz Ring oscillator).
this beating is only for monitoring purpose, in order to manually adjust the laser frequency at the beginning of a run. |
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correct parameters for locking the FP-cavity, posted by Ronic Chiche at ThomX igloo about software
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Today, we restarted the FP-cavity locking, after 3 weeks without using it.
those 3 weeks have been used to set the machine ring at the new (better) frequency : 500.067MHz (corresponding to a change of -183kHz)
or 33.3378MHz in fondamental frequency (corresponding to a change of -12.2kHz) |
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correct parameters for locking the FP-cavity, posted by Ronic Chiche at ThomX igloo about software
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this morning I solved the problem of the 33MHz frequency beating which should be ~12kHz between the generator (at the new frequency 33.3378MHz) and the
laser cavity frequency (still at the old frequency which is 33.35MHz)...
the generator providing the 33MHz frequency has 2 channels, and only one was set at the proper frequency ! |
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Laser and FP cavities frequency adjustment, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics
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at the beginning of the procedure, the frequency gap between the new Ring 33MHz frequency (33.3378MHz) and the laser/FP cavities frequency was 12.33kHz
=> the Smaract motor position was at +100µm
=> the FP cavity motor Mot.03 position was at -358 720 steps |